The Journal of Bone and Joint Surgery (American). 2006;88:58-62.
doi:10.2106/JBJS.E.01286
© 2006 The Journal of Bone and Joint Surgery, Inc.
Basic Science of Pain
Joyce A. DeLeo, PhD
Corresponding author: Joyce A. DeLeo, PhD Dartmouth-Hitchcock Medical
Center and Dartmouth Medical School, Neuroscience Center at Dartmouth,
Departments of Anesthesiology and Pharmacology, HB7125, Lebanon, NH 03756.
E-mail address:
joyce.a.deleo{at}dartmouth.edu
The author did not receive grants or outside funding in support of her
research for or preparation of this manuscript. She did not receive payments
or other benefits or a commitment or agreement to provide such benefits from a
commercial entity. No commercial entity paid or directed, or agreed to pay or
direct, any benefits to any research fund, foundation, educational
institution, or other charitable or nonprofit organization with which the
author is affiliated or associated.
The origin of the theory that the transmission of pain is through a single
channel from the skin to the brain can be traced to the philosopher and
scientist René Descartes. This simplified scheme of the reflex was the
beginning of the development of the modern doctrine of reflexes.
Unfortunately, Descartes' reflex theory directed both the study and treatment
of pain for more than 330 years. It is still described in physiology and
neuroscience textbooks as fact rather than theory. The gate control theory
proposed by Melzack and Wall in 1965 rejuvenated the field of pain study and
led to further investigation into the phenomena of spinal sensitization and
central nervous system plasticity, which are the potential pathophysiologic
correlates of chronic pain. The processing of pain takes place in an
integrated matrix throughout the neuroaxis and occurs on at least three
levelsat peripheral, spinal, and supraspinal sites. Basic strategies of
pain control monopolize on this concept of integration by attenuation or
blockade of pain through intervention at the periphery, by activation of
inhibitory processes that gate pain at the spinal cord and brain, and by
interference with the perception of pain. This article discusses each level of
pain modulation and reviews the mechanisms of action of opioids and potential
new analgesics. A brief description of animal models frames a discussion about
recent advances regarding the role of glial cells and central nervous system
neuroimmune activation and innate immunity in the etiology of chronic pain
states. Future investigation into the discovery and development of novel,
nonopioid drug therapy may provide needed options for the millions of patients
who suffer from chronic pain syndromes, including syndromes in which the pain
originates from peripheral nerve, nerve root, spinal cord, bone, muscle, and
disc.

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